Method and apparatus for coating metal strip



Sept. 11, 1934. E. l.. DAVENPORT .n 1,973,431 METHOD AND APPARATUS FOR COATING METAL STRIP Filed DeQ. 7. 1932 ZShSQtS-Sheet l INVNTOR Lam/mf. v

Um/Lm@ im sept 11, 1934- E. l.. DAVENPORT METHOD AND APPARATUS FOR COATING METAL STRIP Filed Dec. 7. 1932 2 Sheets-Sheet '2 Patented Sept. 11, 1934 PATENT OFFICE METHOD AND APPARATUSFR COATING METAL STRIP Edward L. Davenport, New Castle, Pa., assignor to Johnson Bronze Company, New Castle, Pa., a corporation of Pennsylvania i Application December 7, 1932, Serial No. 646,135

7 Claims.

My invention relates to a method and apparatus for coating and, in particular, to the coating of metal strip. The specific application of the invention which I now contemplate is the coating of steel strip with non-ferrous metal having a high fusing temperature, such as bronze or brass, for the purpose of making steel backing bearings with linings of suitable bearing tained at the point of application of the bronze` to the steel so that the molten bronze will penetrate the surface pores of the steel to form an intimate union therewith. 'I'his vcondition has heretofore not been obtained, so ,far as I am aware, in a continuous coating process V or apparatus.

I have invented a method and apparatus capable of satisfactorily providing a continuous steel strip with a coatingmf-bronze or other bearing metal of suitable thicknessto form a bearing bushing.- In accordance with my invention, yI providea source of molten bronze adjacent a continuously moving steel strip. I provide means for heating the strip as it vmoves past the source of molten., metal, and means for conducting a continuous;y stream of the latter to the strip. In order to prevent 'oxidation of the steel strip, I enclose it in a chamber having a non-oxidizing atmosphere. I thus prevent the formation of an oxide layer on the steell which would preventperfect adherence of the bronze layer applied thereto.

For a complete understanding of the` invention, reference is made to the accompanying drawings illustrating present preferred embodiments thereof.

In the drawings- Y v Figure 1 is a sectional view which is largely diagrammatic, illustrating one formof apparatus for'carrying out the method of my invention; i

Figure 2 is a partial view showing a portion of the apparatus ofv Figure 1 to enlarged scale; Figure 3 is a sectional view taken along the bearings.. Driving means of any -convenient character (not shown) are provided for the pinch rolls 11. The rolls make a substantially gas-tight joint with the wallsv of the housing. Idler. pinch rolls 12 are similarly mounted` at the other end of the housing 10 which isvthe entrance end. 'I'he pinch rolls 11 and 12 provide means-for drawing a length of steel strip 13 through the housing 10. Within the housing a guide 14 having a trough-shaped depression therein is provided for directing and supporting the strip.

A supply pipe 15 connects with the housing 10 toadmit -inert gas or other non-oxidizing or erably, the gas in the housing is maintained under a pressure slightly above that of atmosphere, and any leakage between the housing and pinch rolls is immediately made/up by additional gas supplied through the pipe 15. J

A bronze pot 16 mounted above the housing 10 provides a source of molten metal for application to the continuously moving strip 13. Preferably, the bronze is melted in any, suitable type of deoxidizing atmosphere to the housing 10. Preffurnace and poured into the pot 16. Heating means should be provided for the pot 16 to make up radiation and other losses, but the nature of such means is not material to the present inven,

tion. As an example thereof, I have shown a high frequency induction coil 17 which operates in a well-known manner to produce eddy cur- 4rents in the molten mass of metal which maintain the mass at the desired degree of tempLerature.

In addition to maintaining the mass of metal in the pot 16 at the proper temperatura-it' is Aalso important to maintainthat portionpof the metal flowing through the passage 19 at a temperature such that it will 'bond properly with the steel strip 13 as it flows thereupon. For this purpose, I provide a generator 20 connected tln'ough a no'vo1tage relay 21 and a sliding con- Extending downwardly from the pot 16 and C90 tact of any suitable construction to the pinch l rolls 12. The no-voltage relay 21 is of standard construction and is employed to open Ithe genp,

erator circuit upon failure of the voltagetherein to prevent shunting of other circuits to be deten metal in the pot. 16. A circuit is completed through the molten metal in the pot and that in the passage 19 and the strip 13 between the spout 18- and the pinch rolls 12, so that current iiows through said circuit. The effect of this current is first to preheat the strip 13 as it passes through Ithe housing 10; second, the current also has the effect oflheating the metal in the passage 19 of the spout 18. The increased resistance of that portion of the circuit leads to the generation of a major portion of the heat therein, so that the molten metal as it flows through the Aspout onto the strip 13 is heated to the proper degree which, of course, is susceptible of Yeasy control by varying the current supply of they generator 20.

The guide 14 supports and directs the strip 13 as it movesL through the housing 10 and under the spout 18. With the conditions as described, of course, the strip 13 is preheated in traveling from the'pinch rolls 12 to the spout 18 Where it receives its layer of molten bronzev indicated in Figure 2 at 23. Both the steel strip 13 and the bronze coating 23 are prevented from oxidation by the deoxidizing or non-oxidizing atmosphere supplied through the pipe 15. After the strip has passed beneath the spout 18, it is further heated to maintain the bronze layer molten for a suicient length of time to permit proper alloying thereof with the steel base. This heating is accomplished by a generator 24 ,connected through a no-voltage relay 25 and a sliding contact to the pinch rolls 11. The generator 24 is also connected to the pinch rolls ,12.- Heating current is thereby supplied tothe full length of the strip 13 between the pinch rolls 11 and 12 and to both the coated and uncoated portions thereof. The generator 24 also aidsin the preheating of the strip 13, as well as maintaining the bronze layer at the proper temperature for thel required interval. K

The pinch rolls 11 and 12 are preferably water-cooled, as indicated, by any convenient means to Aprevent their attaining excessive temperatures. The rolls 11, furthermore, exert a cooling effect on the coated strip so that the bronze layer appliedthereto hardens and forms a permanent bond with the steel base. l Referring now to Figure 4, I have illustrated a modiied form of apparatus for carrying out the method, which is similar in some respects to the apparatus shown in Figure 1. Corresponding elements are indicated by the same-reference numerals. The features of the apparatus 'of Figure 4 differing from those of Figure 1 are the means for preheating the steel 'strip `indicated at 13, and the means for maintaining' fluid the molten metal in the discharge spout of the pot 16. f

As shown in Figure 4, a conduction heater 26 is disposed within the housing 10 and is connected to any suitable source of current. The

strip 13 passes through the heater 26 and 'its temperature is thereby raised to the proper point for the `application of a layer of molten bronze. The bronze pot 16 in Figure 4 has a discharge vspout 27 with a central passage 28 therethrough /of cross section similar to the passage 19 of Figure 1. For maintaining the 'fluidity of molten bronze passing through the spout 27 and for-further heating the strip 13, I provide a highfrecuency induction coil 29 having portions disposed above and below the spout and strip. vThe effect of such coil, of course, is to 'induce eddy currents in the bronze in the passage 28 and the strip 13, which heat the metal to the desired degree. The guide 14 may be of a high temperature alloy metal so that it also is heated by the induced currents.

'I'he operation of the apparatus shown in Figure r4 is substantially the same as that of Figure 1. The strip 13 is drawn through the housing 10 by means of the driven pinch rolls l1, is preheated by the heater 26, and is then given a layer of molten bronze delivered through the spout 27. The bronze layer' as it is delivered and the strip 13 as it approaches the spout 27 are heated by induction to the proper point. The proper brazing temperaturefor lbronze is about 2200 F., and if the steel strip is heated to this temperature or slightly therebelow, a satisfactory alloying or welding of the bronze to the steel will occur. A

It will be apparent from the foregoing description that the invention provides highly useful means for applying a coating yof bearing metal to a continuous steel strip at a high rate and at very low cost, The base or backing strip can be obtained in long lengths so that the operation of the coating apparatus can be made fairly continuous. By maintaining the molten metal at the proper brazing temperature at the point where it engages the backing strip, a satisfactory union therebetween is assured. The flow of molten bronze from the bronze pot may,

"of course, be controlled by any suitable means not shown. In case of failure of the voltage in anyjof the .heating circuits of Figure 1, the no-voltage relays immediately operate to open the circuits and prevent shunting of the other circuits in parallel therewith. The preheating of the steel strip prevents the possibility of chill- `ing the bronze upon contact withn the strip,

which would otherwise occur. Since the pre- A heated strip is maintained in a non-oxidizing -two preferred embodiments of the invention, it

is/obvious that numerous changes therein may be made without departing either from the spirit of the invention or-the scope of thev appended claims.

I claim:

' 1. In a method of coating strip, the steps including subjecting a continuous strip to a preheating operation, supplying a non-oxidizing atmosphere in the vicinity of the preheated strip, delivering a stream of liquid coating material onto one side of the strip, maintaining the other side of the strip substantially free from contact with said stream, and furtherr heating the strip and coating after application of the latter to the strip.

2. Apparatus for coating strip comprising strip-feeding means, means for delivering a stream of molten coating material to one' side of a moving strip actuated by the feeding means, means for heating the strip prior to receivin'g ,the coating -materiaL means for supporting the strip at the point of delivery of said stream, and means for heating said stream at said point of delivery.

3. In a coating apparatus, strip-feeding means, a guide for supporting the strip as it is being fed, a source of coating material above the strip,

a spout from said source extending to a point` over said guide, and means for electrically heating said strip, the coating material in said spout and the source of coating material, including aY contact projecting into the latter.

4. In a coating apparatus, strip feeding means,

a guide supporting the strip as it is being fed, a source of coating material adjacent thereto, and a spout extending from said source to a point above said guide, of means for supplying heating current to the strip approaching said guide, and means for electrically heating the coating material adjacent the point of delivery to the strip, including a contact projecting into said source.

5. In a coating apparatus, strip feeding means,

. a container for coating material having a spout of delivery of the former.

7. Apparatus for coating a strip with a conducting material including a container for the material, strip advancing means, a passage for material to flow through from the container to the strip, and means for electrically heating the material, including a contact projecting into the container.

EDWARD L. DAVENPORT. 

